# coding=utf-8

"""
Given a binary search tree and a node in it, find the in-order successor of that node in the BST.

The successor of a node p is the node with the smallest key greater than p.val.



Input: root = [2,1,3], p = 1
Output: 2
Explanation: 1's in-order successor node is 2. Note that both p and the return value is of TreeNode type.

Input: root = [5,3,6,2,4,null,null,1], p = 6
Output: null
Explanation: There is no in-order successor of the current node, so the answer is null.


"""


# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def inorderSuccessor(self, root, p):
        """
        :type root: TreeNode
        :type p: TreeNode
        :rtype: TreeNode
        """

        def minNode(node):
            while node.left:
                node = node.left
            return node

        def searchP(root, p):
            if not root or root.val == p.val:
                return None
            else:
                succ = None
                while root != None and p.val != root.val:
                    if p.val < root.val:
                        succ = root
                        root = root.left
                    else:
                        root = root.right
                return succ

        if p.right:
            return minNode(p.right)
        else:
            return searchP(root, p)
